This invention is related to a waveguide device which supports multiple signals having varying frequencies and polarities. More specifically, this invention relates to a multi-port multi-band transceiver interface assembly in which signals having a first band with one or more polarities are separated from second band signals (having one or more polarities) where the second band signals are supported by a waveguide structure having an input port and an output port which lie substantially in the same plane which is generally perpendicular to an input feed for the first and second bands.
As technology advances, an increasing number of reflector antenna applications, including satellite and other antenna type applications, require complex multi-port (4 or more) assemblies to support the multiple polarities and multiple frequency band signals that are used in such assemblies. Typically, these assemblies are referred to as waveguides. The complexity increases and certain difficulties arise when in addition to the input port in which the signals are all received, these systems also further require signals having multiple polarities to be transmitted and signals having multiple polarities to be received. For example, the system may require transmitting on 2 polarities and receiving on 2 polarities at the same time.
In response to such needs, assemblies have been developed to process such signals; however, these conventional assemblies have a number of associated deficiencies. For example, the conventional assemblies have been very costly and also have degraded performance in the form of degraded cross polarity rejection. In addition, these assemblies are typically inconveniently packaged and a mechanically bulky which causes the assemblies to be difficult to install and difficult to adjust the polarity. For example, four-port combiner devices with symmetric branching are available. These devices typically include a common port in which two input bands (high and low frequency) are inputted into the input port and then separated from one another. The low band is separated from the high band by using four lower ports which separate the two polarities of the low band. Thus, two lower ports are used for each polarity and the respective bands are sent upwards within four separate symmetric waveguide members. These four separate waveguide members comprise elongated members which each share a common axis with the input signal so that symmetry of the signals is maintained. Because the device has multiple ports, the device is relatively very long and mechanically complex because the feed antenna is connected to the common port such that it lies along the same axis as the transmit or receive elements. This results in a bulky assembly which is unsuitable for many applications. Other conventional assemblies have designs which require the heavy transmit radio to be mounted off the center feed horn axis, making it more difficult to support, and adjust, and less aesthetically attractive. Some assemblies which are compact and keep the transmitter in-line with the feed horn suffer from reduced performance due to asymmetries in the design of these assemblies. For example, some of these assemblies are somewhat limited to dual band applications where the two frequency bands are separated a considerable band width apart from one another. This limits the scope of application of the assembly.
Accordingly, it is desirable to provide a waveguide assembly having a common port which supports band signals having different frequency bands and each containing one or more polarities, wherein one of the band signals is separated from the other band signal in a manner which permits the design of the assembly to be compact and symmetric.
According to one embodiment of the present invention, a waveguide assembly is provided and includes a common input waveguide aligned along a first axis. The input waveguide supports two frequency bands each having one or more polarities. The frequency bands, namely high and low band signals, are typically supplied using a feed horn which is coaxially aligned with the input waveguide. The input waveguide preferably includes coaxial inner and outer members with the inner member being configured to carry a high band signal (one or more polarities). The inner member is constructed so that the high band signal is carried and passed straight through the inner waveguide preferably without any separation between the one or more polarities. The outer member supports the low band signal having one or more polarities.
The waveguide assembly includes an output waveguide for supporting and discharging the low band signal (one or more polarities). The output waveguide extends along a second axis which is parallel to the first axis containing the input waveguide but is displaced therefrom. In other words, the low band signal is received at one location and discharged at a second location spaced therefrom but axially aligned therewith. In this manner, the low band signal is separated from the high band signal and carried to the output waveguide where it is discharged from the waveguide assembly.
In order to accomplish this the waveguide assembly, according to one embodiment, has first and second waveguides connecting the input waveguide to the output waveguide. The first and second waveguides are disposed substantially perpendicular to the input and output waveguides such that the low band signal is fed into the outer member and then separated therefrom by being carried within one or more planes defined by the first and second waveguides before being discharged through the output waveguide.
Accordingly, the present invention provides a waveguide assembly which is compact and preferably symmetric in nature so that the phase of the low band signal does not change as measured at the input waveguide and the output waveguide. In this way, the phase length and orientation of the first and second waveguides are carefully controlled so that a phase difference does not result. In other embodiments, the first and second waveguides may be configured so as to introduce a phase difference if this is desired in a given application. In contrast to conventional waveguide devices, the first and second waveguides preferably lie within one or more planes which are substantially perpendicular to both the input and output waveguides and therefore the present waveguide assembly may be conveniently sandwiched between two components, e.g., the feed horn and a radio, during use of the waveguide assembly. This is in contrast with conventional devices which comprise elongated structures aligned along the same axis as the feed horn and the other component, such as the radio.
In one embodiment, the assembly also includes third and fourth waveguides in which the first, second, third, and fourth waveguides intersect one another at a first location and at a second location. The first location is where the input waveguide is coupled to each of the waveguides and the second location is where the output waveguide is coupled to each of the waveguides. The different polarities of the low band signal are separated from one another at the first location by being launched into a number of paths which each connects the input waveguide to the output waveguide. Next adjacent paths are spaced at a predetermined angle relative to one another and preferably, the predetermined angle is 90xc2x0 so that one polarity is carried within one path and the other polarity is carried within the path which has a 90xc2x0 orientation therefrom.
In this exemplary embodiment, each waveguide defines a respective path and has a phase length associated therewith. The paths are spaced apart so as to support both the first and second bands. The first and third paths, which are preferably spaced 180xc2x0 apart, carry the same polarity low band signal and the second and fourth paths, also spaced 180xc2x0 apart, carry the other polarity low band signal. The paths which are spaced 90xc2x0 apart therefore carry low band signals of different polarity. It is generally preferable to not introduce a phase difference between the different polarity low band signals as the signals are carried through the waveguide assembly. In order to accomplish this the phase length and orientation of the waveguides are carefully tailored so as to maintain a level of symmetry.
In one aspect of the invention, the different polarity low band signals are launched into respective waveguides in the same first plane in which the signals are later recombined before being discharged through the output waveguide. Because the signals are launched and recombined in the same first plane, a level of symmetry is achieved. In addition and importantly, the phase lengths of each waveguide is preferably equal to the others so as to also introduce further symmetry into the waveguide assembly. In several embodiments, the waveguides have a cross-over orientation which permits the phase lengths of each waveguide to be equal to one another. At locations other than the first and second intersections where the first waveguide member crosses over the second waveguide, each of the first and second waveguides includes a bridge-like section which extends out of its plane and permits the other of the first and second waveguides to pass thereunderneath. After the respective first or second waveguide passes thereunderneath, the respective waveguide returns to its plane and continues on to the output waveguide. This design achieves equal phase lengths resulting in greater symmetry introduced into the waveguide assembly, while keeping the first and second waveguides within a defined plane. A similar configuration for the third and fourth waveguides is provided.
In other embodiments according to the present invention, the phase lengths and/or structures of the waveguides may be altered so as to introduce a phase difference between the first polarity paths and the second polarity paths.
Other features and advantages of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.